Bacterial co-cultivation for the degradation of polystyrene plastics

Polystyrene (PS) is a polyolefin plastic that is used extensively in food packaging. The chemical structure of PS is extremely stable owing to its C-C backbone and styrene rings, making it highly resistant to biodegradation, which causes serious environmental pollution and health threats. Although certain microorganisms have been reported to degrade PS waste, most studies have focused on the changes in the molecular weight and surface structure of plastics. These slight degradation phenomena make it extremely difficult to detect the degradation products, thus challenging the definitive demonstration of PS degradation. This study investigated the co-cultivation of the polyolefin plastic-degrading bacterium Raoultella sp. DY2415 and the benzoic acid bioconversion strain Pseudomonas putida KT2440-ΔRBC. BA is a possible degradation product of PS and can be converted by P. putida KT2440-ΔRBC into the high value-added compound muconic acid (MA). After co-cultivation, MA was detected in the medium, indicating that Raoultella sp. DY2415 degraded PS and generated BA, which was subsequently utilized by P. putida KT2440-ΔRBC for MA synthesis. This study demonstrated the biodegradation of PS and the synthesis of MA through a fully biological process, thereby promoting the circular economy of plastics.